Knife rest for a band shaped splitting knife



April 1,1969 F. FLEKA" 3,435,540

KNIFE REST FOR A BAND SHAPED SPLITTING KNIFE I Filed Nov. 21, 19675761x777 Yer 6 f/e K62,

I NVE N TOR.

United States Patent O 3,435,640 KNIFE REST FOR A BAND SHAPED SPLITTINGKNIFE Frantisek Flekac, Krnov, Czechoslovakia, assignor to Strojosvit,Narodni Podnik, Krnov, Czechoslovakia Filed Nov. 21, 1967, Ser. No.684,864 Claims priority, application Czechoslovakia, Nov. 21, 1966,7,380/66 Int. Cl. C14]: 1/18 US. CI. 6910 1 Claim ABSTRACT OF THEDISCLOSURE A knife rest for a band shaped splitting knife of a splittingmachine for leather, hides and similar fiat material, said knife restautomatically adjustable to different conditions of the splitting knifein operation, securing thus a contact between the rear surface of theknife and the active contact surface of the knife rest along a largecontact area said rest having a curved face contacting its backingmember to facilitate rotation of the rest against its backing member.

BACKGROUND OF INVENTION Splitting machines for leather and hides arevery important in the leather industry as the economy of manufacturingdepends mostly on a proper splitting operation. The most importantelement for the operation of a leather splitting machine is thesplitting knife, its correct guiding and grinding. At present splittingknives from relatively thin steel, connected to an endless band, aregenerally used for this purpose. The knife is guided between lateralgibs and is supported by differently arranged rests, against which theknife leans with the width of its rear surface. There is a number ofdifferent systems of distribution and of adjustment of such knife rests.

In order to safeguard a correct operation of the knife, which moves at arelatively high speed, it is necessary to provide a correct inclinationof the respective driving and tensioning rollers, in order to achieve inthe course of operation of the machine automatically the contact of theknife with the knife rests. This of course causes a bending of the knifeand the result of this bending is that there is frequently only a pointcontact between knife and rest.

A point contact between knife and rest is furthermore caused due to acertain clearance of the guiding, whereby the rest is moved due tofriction in the course of operation of the machine. In addition duringthe life time of the knife, the bending of the knife is equallychanging, it is different for a new knife and for a used knife and isalso different if some different technology has been used formanufacturing the knife. It should be also noted, that the sense ofmotion of the knife is frequently reversed so that even if for one sensesome contact area is created, a point contact is again established forthe reverse sense.

The point contact between knife and rest, which particularly occurs onthe rests on both extremities at a high pressure and speed,substantially affects the life time of the knife. Due to a concentratedpressure on the rear surface of the knife a high local stress of thematerial of the knife is created, resulting in cracks, which lead to arupture of the knife, and which practically occur only on the rear partof the knife.

Rests with hard metal on the active contact surface have been also usedwith increasing outputs of the machines. The life time of the rests hasbeen prolonged, but the stress of the rear part of the knife has beenPatented Apr. 1, 1969 rather increased. Rollers have been also usedwhere the operating conditions of the machine allowed such anarrangement. But due to the high stress imposed on these rollers bothdue to the speed and character of application, this solution has only alimited significance.

SUMMARY OF THE INVENTION It is an object of this invention to eliminatethese drawbacks, what is achieved by providing the active contactsurface of the rest of the splitting knife on an element capable to bedeviated, which element is supported by an adjustable part of the restcomprising a circular part, the centre of curvature of the circular partof this element situated in front of the active rest surface.

DESCRIPTION OF DRAWINGS An embodiment of the object of this invention isshown on the accompanying drawings where FIG. 1 is an elevation of thewhole arrangement, FIG. 2 a detail of the knife rest and FIG. 3 apartial sectional view of a part of the splitting machine with theknife.

DESCRIPTION OF PREFERRED EMBODIMENT The knife 1 of the splitting machinerests with its rear part against the active supporting surface 2 of anelement 3 capable to be deviated. Hard metal may be advantageously usedon the active supporting surface 2. The element 3 capable to be moved issupported by its rear circular part 7 by an adjustable supporting part 4of the rest, guided laterally between gibs 5. The adjustment of theadjustable part 4 of the rest in this case accomplished by means ofscrew bolts 6. Gibs 11 and 12 (see FIG. 3) guide the knife 1 in thedirection, in which pressure is transmitted to the knife 1. In the casegiven they simultaneously enable by their shape the lateral guiding ofthe element 3 capable to be moved. The lower gib 11 is fixed on the rearsupport 13 of the splitting machine. The leather is supplied by feedingrollers 14 and 15 towards the knife 1 and splitting is accomplished dueto the action of the sharp cutting edge at place 16. A driving roller 8transmits motion to the knife 1 which is tensioned by the tensioningroller 9. The center S of curvature of the circular part 7 is situatedin front of the active supporting surface 2 in order to achieve in thecourse of operation of the machine, where the knife moves in itslongitudinal direction, a cooperation of the forces of friction toadjust automatically the element 3 capable to be deviated into its mostadvantageous position, so that the force acting on the rear surface ofthe knife is uniformly distributed along the whole active supportingsurface 2.

The opposite case, i.e. a point contact between knife 1 and the activesupporting surface 2 would result if the center S of curvature of theelement 3 would be in front of the rear surface of the knife 1, forinstance if the center of rotation of the element 3 would be the place,where the element leans against the adjusting screw.

Pressure of the knife 1 against the element 3 capable to be moved isgenerated not only due to pressure of the split material 10 which is fedtowards the knife 1, but also in the course of idle running due to arelative inclination of the rollers 8 and 9 as already mentioned, asotherwise the knife 1 could leave the rollers 8 and 9.

As the coefficient of friction between the knife 1 and the activesupporting surface 2 of the element 3 capable to be deviated isrelatively small, the force, which tends to force the element 3 towardsthe adjustable part 4 of the rest prevails, what equally cooperates foran automatic adjustment of the element 3 into its most advantageousposition if the center of curvature of the circular part 7 is properlychosen.

If the adjustment of the machine, the tension of the knife, thedirection of motion of the knife or other conditions are changed, thearching and deviation of the knife from the machine axis are changed,but the element 3 capable to be moved adjusts itself automatically sothat the rear surface of the knife is in the course of operation subjectto a minimum stress and the active supporting surface 2 of the element 3capable to be deviated is stressed uniformly so that wear of bothelements is reduced to a minimum and requirements for adjustment areequally substantially reduced.

I claim:

1. Knife backing rest for a knife of a splitting machine for leather,hides and similar fiat material, said knife in the shape of an endlessbend With a cutting edge and 15 rection towards and away from said bandknife; means for adjusting the position of said supporting part; saidsupporting part provided with a circular supporting surface for saidelement capable to be moved; the curvatures of both said circular partsbeing equal and having a common center of curvature situated in front ofthe active contact surface between the band shaped knife and saidelement capable to be moved.

References Cited UNITED STATES PATENTS 617,666 1/1899 Whipple 69-10909,157 1/1909 Chilson 69-40 2,524,013 9/1950 Hall 6910 2,804,141 8/1957Danner 6910 FOREIGN PATENTS 166,699 7/ 1921 Great Britain.

ALFRED R. GUEST, Primary Examiner.

US. Cl. X.R.

